Conventionally, transmission equipment has been introduced in communication carriers for transmitting TDM (time-division multiplex) channel signals. In recent years, however, mainstream of the traffic data carried by communication systems has been shifted to data having a packet format.
Today there is one type of such a network, as shown in FIG. 1, in which an IP packet is routed by a router or aggregator 201 or the like in an ISP (internet service provider) 200. Long-haul transmission of such a packet is then carried out using transmission equipment 101 provided by a communication carrier 100.
Here, packet signals multiplexed into STS-n (n=1/3/12/48) are transmitted in a long distance through transmission equipment 101 provided in carrier 100. The signals are conveyed through a predetermined path (or a physical channel) dedicatedly connected one-to-one (point-to-point) by a cross-connect portion (routing means). In such a manner, packet traffic is conveyed through a TDM channel without need of distinguishing the information unit, ‘packet’.
However, when 1-to-n (i.e. point-to-multipoint) connection is desired for packet traffic, there are required extremely large number of cross-connect lines so far as the above-mentioned type of transmission is employed. In order to meet such traffic requirement, transmission equipment of this type is not economically advantageous.
One method introduced in earner 100 to cope with the aforementioned problem is shown in FIG. 2. IP traffic 300 is terminated and then is lead to an aggregator router 102, which are additionally provided and in which traffic signals are concentrated or routed on a packet-by-packet basis, so that the number of connection lines for 1-to-n (point-or-multipoint) connection between the nodes can be decreased.
To implement the above-mentioned method, however, it is necessary for carrier 100 newly to introduce aggregator or router 102. This necessitates additional capital investment, reservation of installation space, and measures to cope with the difference of maintenance method.